Can't select edges after dissolving and using loop cut tool
Those dark orange edges are on a separate object which is selected outside of edit mode.  Either you had both objects selected when you went into edit mode, or you Ctrl + xlicked it while in edit mode, or (more likely) you inadvertently disconnected it by hitting P with that geometry selected.

Either way, you can fix this by exiting edit mode and joining the two back together again with Ctrl+J (with both still selected).

If you need to reconnect the edges, select the vertices in pairs and merge them with Alt+M.  (Selecting all with A and hitting W > Remove Doubles may also work to reconnect at least some of the geometry.)